The Internet protocol multimedia subsystem (IMS) network architecture is defined by the Third Generation Partnership Project (3GPP) as a new mobile network infrastructure that enables the convergence of data, speech, and mobile network technology via an IP-based infrastructure. IMS is designed to deliver Internet-based content to mobile phone users. IMS carries signaling and bearer traffic over the IP layer and operates as a routing engine or session control application that matches user profiles with appropriate call/session-handling servers, and then routes the call or session to the appropriate destination. The architecture includes the capability to add, modify, or delete sessions during an existing multimedia session, or a wireless call. This opens possibilities of “blended” services that involve simultaneous voice, data, and multimedia not only for wireline but for wireless calls as well. Application servers are nodes on the IMS network that provide these services.
One service made possible by the IMS architecture is conference calling, in which the traditional concept of a call as a connection between two endpoints, e.g., caller and callee, is extended by allowing multiple parties to be connected to or disconnected from the call. For example, the IMS network may include a node, such as an application server, that provides the conference call service. All parties to the conference call are routed through this node, which acts conceptually like a simple repeater: if the application server receives a packet, representing a portion of voice data for example, from any party to the conference call, the application server sends copies of that packet to every other party to the conference call. Adding a party to the call is as conceptually simple as adding another name to the list of parties to the call. Both wireless and wireline users may be parties to the call, since calls from both types of users are ultimately converted to packets in the core IMS network.
Other services enabled by the IMS architecture include presence services, which provide presence information for a user or subscriber of a network. Presence information is a status indicator that conveys ability and willingness of a user to communicate. For example, a user's client, such as a cell phone, personal digital assistant (PDA), mobile computer, etc., may provide presence information to a presence server on the IMS network. The presence server determines the presence state of the user, potentially making that information available to others, who may poll the presence server to determine the state of the user or who have requested that the presence server notify them of any change in the user's presence state. Presence information is widely used for instant messaging and voice over IP, to determine availability of users in a “friend's list”, for example.
However, one of the challenges facing IMS for providing blended services is that there is not an established way to pass the status of a mobile end device in a wireless domain directly to an application server in an IP domain. This hinders an application server from providing those services, such as presence services, call forwarding, auto attendant services, and others, that depend on the device status, to the wireless client.
Accordingly, there exists a need for systems, methods, and apparatus for communicating the state of a wireless user device in a wireless domain to an application server in an internet protocol (IP) domain.